If SF gets Rivers, it elminates their need for a QB, and if they trade the pick to SD it won't be used on a QB. Both of those teams need WR and Edwards is at the top of most draft boards right now.

Great Blue North Draft Report's most recent mock is based on that assumption and it points out a couple of interesting things:
1 - Both QBs will probably still go top 10 because there are several teams that need QBs.
2 - If Edwards is gone at #1, will Minn reach for Williamson?

That's a trade that won't happen. SD has spent 14 Mill on Rivers bonus, they would need to sign Breez to a long term and that would cost 14 Mill in bonus or more and then they have the first pick to sign which would get something like 14 mill in bonus. That's a boatload of money not to mention the cap hit SD would get. Great deal for SF though.